At present, magnetic multilayer films are being proposed as a storage element in memories, such as magnetic random access memories (MRAM) and the like. The memory element for the MRAM technology is a patterned structure (memory bit) of multilayer material. The magnetic multilayer material is usually composed of a stack of different materials, such as permalloy (NiFe), cobalt (Co), copper (Cu), tantalum (Ta), etc. and may include some insulator like materials, such as Al.sub.2 O.sub.3, etc. A typical stack may contain as many as ten different overlying layers of these materials. To fabricate a storage element, it is necessary to deposit the materials in overlying blanket films, layer by layer, and then pattern the films into appropriate structures.
At present, the patterning is accomplished by a process called ion milling, which involves physical sputtering of the layers by an argon ion beam. However, ion milling has a serious drawback called sidewall redeposition. This means that a fraction of the removed material actually redeposits on the sidewalls of the remaining magnetic multilayer stacks. This inherent redeposition on the sidewalls gives rise to "ear-like" structures which extend upwardly from the sidewalls above the upper surface of each of the multilayer magnetic stacks. These "ear-like" structures cause, among other things, electrical shorts and bit irreproducibility. In addition to this problem, ion milling is generally not considered to be a manufacturable process.
Thus, it would be highly desirable to have a process that overcomes these problems.
It is a purpose of the present invention to provide a new and improved process of patterning magnetic multilayer films.
It is another purpose of the present invention to provide a new and improved process of patterning magnetic multilayer films which results in clean structures free of sidewall redepositions.
It is still another purpose of the present invention to provide a new and improved process of patterning magnetic multilayer films which is manufacturable.